(1) Field of the Invention
The present invention relates to a light guide plate and a side-emitting backlight module having the same, and more particularly relates to a light guide plate with a micro-structure and a side-emitting backlight module having the same.
(2) Description of the Prior Art
A light guide plate is an important component affecting the light efficiency of a side-emitting backlight module. The light guide plate is applied to the side-emitting backlight module to transform the light beam from a point light or a line light source to an uniform plane light and then enhance the uniformity and brightness of the plane light based on the light uniform ability of a diffusion film and light concentration ability of a brightness enhancement film. The light guide plate has two types of appearance, wedge and flat. Generally, a notebook computer adopts wedge type due to considering the space allocation, while a liquid crystal display (LCD) Monitor and a LCD TV use flat type mostly.
Refer to FIG. 1A for a schematic view of a side-emitting backlight module 100 having a conventional light guide plate 100. The side-emitting backlight module 100 includes a light guide plate 120, a light source 140, a brightness enhancement film 160 and a diffusion film 180. The light guide plate 120 is a wedge transparent board, mainly used in conducting the light direction to enhance the brightness of a liquid crystal panel and control the uniformity. The wedge light guide plate 120 generally includes a thick end-surface 122, a thin end-surface 124, a bottom surface 126 and a top surface 128. During the assembly of the side-emitting backlight module 100, the bottom surface 126 of the light guide plate 120 usually faces down and the top surface 128 faces up, while the brightness enhancement film 160 and the diffusion film 180 are disposed on the top surface 128. In FIG. 1A, the bottom surface 126 is set upwards to illustrate the micro-structure.
The bottom surface 126 of the light guide plate 120 forms a micro-structure with a plurality of prisms 126a side by side, called V-cut structure. The light source 140 is disposed at the side of the thick end-surface 122 of the light guide plate 120. Most of the light is transferred to the thin end-surface 124 by total reflection after it enters the light guide plate 120. When the light is transferred to the prisms 126a on the bottom surface 126 of the light guide plate 120, it is concentrated and then emitted out from the top surface 128 (as arrow shows). Thus the light is more uniform after passing through the light guide plate 120 based on the design of the micro-structure.
However, the bottom surface 126 of the light guide plate 120 uses prisms 126a to gather light, so when the line light source or point light source sends light to the light guide plate 120, the incident side of the light guide plate 120 appears bright and dark obviously because of the gathered light, referring to FIG. 1B and FIG. 1C. FIG. 1B displays the distribution of the bright lines 102 of the side-emitting backlight module 100 when the light source 140 is a cold cathode fluorescent lamp 140a (CCFL). FIG. 1C displays the distribution of the bright halos 104 of the side-emitting backlight module 100 when the light source 140 consists of a light emitting diode (LED) 140b. It is necessary to adjust the brightness of the backlight module uniform as the backlight module is presently used in the high brightness.
For the above issues, the conventional method is to fabricate the thick end-surface 122 into a fogging surface which makes the light inside the light guide plate 120 scattered, but it adds fabrication steps, increases cost and thus reduces yield rate indirectly as well as the light use efficiency.